Pioneer SX-450 FM reception

Hello
My SX450 has somehow unstable FM reception when tuning the frequency. It is quite difficult to tune a station exact on the frequency and adjust the frequncey. It tends to drift a little.
Is there something specific I should check first? I know that SX450 can have a bad power switch and I wonder if the switch has something to do with this? However, the dial lights are not flickering and the switch seems to work right.
Any ideas?

Welcome Aboard!

How long does it take to drift? Does it drift only once as the set warms up or does it continue to drift as long as it is turned on?

Actually the set is unstable at the very moment you adjust the frequency and sometimes it's hard to adjust just the right frequency. Once you succeed in tuning the excatly right frequency the set works OK. So perhaps "drifting" is the wrong expression.
I have SX-550 as well and it is much easier to tune. I had to fix and clean SX550's power switch and after cleaning SX550 works fine. My brother owns another SX450 and tuning the frequency is much easier than that with my SX450. It is as easy as tune as my SX550.

First check the 13v supply for stability.

I would put in a new q301 2D313,
C307 100uf 25v smoothing cap for the
D304 zener 512-1N5244B Fairchild 14 V, 0.5W Zener
as well as the zener itself, first.

2sd313:
512-KSC2073TU npn to-220 bce 150v 1.5a 25w 4mhz 40-140hfe $0.66
or
863-MJE15032G npn to-220 bce 250v 8a 50w 30mhz 70hfe $1.30

Hi
Thank you for your message and advice.
I changed C307 and the things got lot better! Thanks!
I will check Q301 and the Zener as well.
I appreciate your help.
Tuomo